Obesity has been associated with a higher risk of mortality, whereas caloric restriction reduces the risk. In this study, we examined how body weight development during life affects lifespan in a mouse model for obesity. Therefore, mice of the Berlin Fat Mouse Inbred line were set on either a standard or a high-fat diet (HFD). Median lifespans of standard diet-fed mice were 525 and 539 days for males and female animals, respectively. HFD feeding further decreased lifespan by increasing the risk of mortality. Our data provide evidence that the highest body weight reached in lifetime has only a minor effect on lifespan. More important is the age when the highest body weight is reached, which was positively correlated with lifespan (r=0.77, P<0.0001). Likewise, the daily gain of body weight was negatively correlated with the age of death (r=-0.76, P<0.0001). These data indicate that rapid weight gain in early life followed by rapid weight loss affect lifespan more than the body weight itself. These data suggest that intervention strategies to prevent rapid weight gain are of high impact for a long lifespan.